This invention relates to an ethylene gas generating composition for use with a catalytic converter of the liquid composition to ethylene gas. The type of catalytic converter recommended is that disclosed in U.S. Pat. No. 3,951,610 issued to one of the co-inventor of this invention.
In the last few years the commercial market for ethylene gas has increased to include not only those uses for the initiation of the ripening of various fruits such as bananas, tomatoes, honeydews, pears, avocados or green citrus fruit such as oranges, lemons, grapefruits, limes and the like all of which has been set forth in the prior patent but also ethylene gas has been found to be useful in the curing of tobacco. This increased use has been in part directly resulting from the increased availability of the supply of ethylene gas in convenient form.
While there are still a number of commercial uses of ethylene gas for which the supply of ethylene is derived from the archaic steel cylinders containing pressurized ethylene, the gas generating apparatus disclosed for the first time as the catalytic converter in the prior patent has made a major contribution to the industry and has avoided the undersirable problems of unsafe storage and handling of the heavy steel cylinders of pressurized ethylene gas.
As described in the prior U.S. Pat. No. 3,951,610 the catalyst in the catalytic generator is preferably activated gamma alumina which theoretically produces in a mole for mole catalytic reaction ethylene by the dehydration of ethanol. Pure ethanol is the only reactive material capable of producing ethylene gas in this generator but ethanol alone is not a legal commercial substance saleable for use in catalytic generators of the type disclosed in the prior patent.
Ethanol is suitable for a number of well-known purposes the primary one, human consumption, makes it a government controlled substance. Therefore, the Bureau of Alcohol, Tobacco and Firearms of the Department of Treasury (BATF) in the United States does not permit the use of ethanol in the ethylene gas generating apparatus of the prior patent unless it has been previously sufficiently denatured to prevent practical separation and preclude potability.
BATF makes available an extensive list of denaturants in various combinations that would be acceptable to the government. Each of the previously known forms or combinations of denaturants generated various by-products such as diethyl ether and the like in the catalytic conversion. These substances were found to increase the flammability potential of the ethylene gas produced and could not be permitted to be released to the atmosphere with the ethylene in any undesirable quantity. The safe production of the ethylene gas in the generator was thus a critical factor. Efforts to improve the direction of the catalytic conversion reaction were unfortunately not successful without significantly reducing the efficiency of the catalyst as measured by the molar proportion of ethylene produced from the ethanol.
The liquid components suggested in the above prior patent for use in the gas generating apparatus were found to poison and contaminate the catalyst so that its efficiency for producing molar equivalent quantities of ethylene gas from ethanol is drastically reduced. Ultimately the catalyst must be replaced in the gas generating apparatus, a time consuming and expensive operation.
Ketones, for instance, were previously thought to be desirable components of the liquid gas generating composition and so were disclosed in the prior patent. It was discovered, however, that ketones such as acetone were a significant cause of the drop in efficiency in the catalytic production of ethylene. However simply omitting the offending denaturant was not a solution because the resulting composition would not be permitted by BATF to be sold commercially unless a denaturing substance acceptable to the government would be included.
The problem therefore surfaced how to meet the government requirements for a denatured liquid composition including primarily ethanol and yet neither poison the catalytic material effecting the generation of ethylene nor produce any harmful by-products through side reactions that would increase the flammability of the ethylene gas produced by the generator.
For instance it has been found that with various compositions dimethyl ether can be produced which would be an explosive hazard to the ethylene gas generated.